RIO DE JANEIRO — Usain Bolt’s only real competition was the clock. He couldn’t beat it. Another gold medal wasn’t such a bad consolation prize.

The Jamaican star romped in what he says is his last Olympic 200-meter race Thursday night, but finished in 19.78 seconds, more than a half-second short of his own world record – the one he said he really wanted to break.

“I’m always happy for the win but I wanted a faster time,” Bolt, who turns 30 on Sunday, told NBC. “I felt good but when I came into the straight, my body wouldn’t respond to me. So I guess it’s just age and all the rounds that’s taken a toll.”

A win is a win, and Bolt has gold medal No. 8 and a third straight 200 victory to go with the same trifecta in the 100. His run for No. 9 comes Friday in the 400 relays. The American men qualified fastest with a season’s-best 37.65 seconds.

All good stuff, but Bolt’s expression as he crossed the finish line told the real story.

Bolt was giving every ounce of effort, grimacing as he approached the line.

He glanced to his left to check out the clock just before he crossed. The time came up and when Bolt saw it, he tilted his head back and yelled.

His record in his favorite race still stands at 19.19. He set it in 2009 at the world championships, breaking the mark he’d set the year before (19.30) at the Beijing Olympics.

Also in track, Ryan Crouser led an American one-two in the shot put, also setting an Olympic record of 22.52 meters to beat the world champion, Joe Kovacs. Tomas Walsh of New Zealand won bronze.

Dalilah Muhammad kept the U.S. total ticking with gold in the women’s 400-meter hurdles and Ashley Spencer added a bronze, with another American 1-2 in that race only just thwarted by Sara Slott Petersen of Denmark. Earlier, Kerron Clement won his first individual gold at the Olympics in the men’s 400 hurdles.

“We are making history out here,” Muhammad said of the U.S. team’s gold rush.

With three days of competition to come, the United States was up to 24 medals in track and field, including eight gold.

For a few short moments on Day 7 of the track and field competition, the U.S. women’s 400 relay team was a little like Bolt: They were the only ones everyone was looking at.

Tianna Bartoletta nestled into the starting blocks in Lane 2 for the U.S. team’s re-run – on their own and against the clock only – after they fumbled the baton in their original qualifier, but got another chance following a protest.

With just the clock and the crowd for company, they took the baton around in 41.77 seconds to knock the slowest qualifier, China, out of the final.

“We were laughing and joking out there,” English Gardner of the U.S. said. “Our coach said before we went out there, ‘It’s just like practice, just the whole world will be watching. Be patient, stay patient with each other, and just do your job.’ ”

Clement was so confident of a first Olympic individual gold in the men’s 400 hurdles that he had his mother, Claudette, bring a star-spangled banner so he could drape it over his shoulders.

“We had a flag at home and I told her to bring the flag. I knew I was going to win,” Clement said.

Boniface Mucheru Tumuti of Kenya took silver, 0.05 behind, and Cuban-born Yasmani Copello of Turkey won bronze in 47.92, both in national records.

Caster Semenya of South Africa, the outright favorite for the women’s 800-meter title, qualified for the final as she breezed to victory in her semifinal heat, pretty much unchallenged, in 1 minute 58.15 seconds.

Sara Kolak of Croatia won the women’s javelin, another first-time Olympic champion like Crouser. Sunette Viljoen took silver and Barbora Spotakova bronze.